Effects of varying tropospheric wind shear on the spectrum of gravity waves generated by tropical convection

A modified version of a two-dimensional, cloud-resolving model presented in Alexander and Holton (1997) is used to simulate gravity waves generated by a tropical squall line. The anisotropic distribution of eastward and westward propagating convectively generated gravity waves in the stratosphere is found to be highly dependent upon the initial background tropospheric wind profile.

In numerous simulations, strength, height, and depth of shear layers in the initial wind profile are varied to elucidate the precise mechanism and source altitude of wave generation. The primary tools for diagnosing wave activity and differences between the eastward and westward waves are calculations of momentum flux carried by the waves and spectral analysis of the wave field. Results point to two source levels of wave origin, one at about 13 km and one below 5 km, and show how small tropospheric wind changes influence the spectrum of stratospheric gravity waves.